STEAMING THE SOIL pi 



high pressure as possible, 80 to 100 pounds being best, 

 and the treatment should continue for one or two hours, 

 depending on the pressure maintained. In experiments 

 conducted in the Spring of 1907, one hour's steaming at 

 80 deg. C. under 100 lbs. pressure gave best results in kiUing 

 both the fungus and the weed seeds. When one section 

 of the bed is treated the pan is lifted and carried to an 

 unsterilized portion and the operation repeated until 

 the entire bed is steamed. 



For the most economical use of fuel and labor in the 

 pan method of steaming, three or possibly four pans will 

 be necessary, according to the width of beds. Estimating 

 the cost of the pans at $15 apiece, the first outlay will be 

 about S50 for set of three pans and connections. 



Thirdly, the drench system or watering with formalde- 

 hyde (formalin). The cost items in this case become re- 

 duced almost to that of cost of material. The best strength 

 appears to be 3 to 3)^ pints or pounds to each 50 gallons 

 of drench, applied at the rate of K to i gallon per sq. ft. 

 of surface. Estimating that formaldehyde (U. S. P. 40 

 per cent.) costs 80c. per gallon, and that a strength of 

 approximately i to 125 (3)^ pints or pounds of formalde- 

 hyde to 50 gallons of water) be used at the rate of i gallon 

 of the solution to each sq. ft. of area, the material to treat 

 one house 30 ft. x 100 ft. (3000 sq. ft.) amounts to ap- 

 proximately $21. The cost of treating the bench space in a 

 house of the same size when either of the steam systems is 

 used will be approximately $15 or S16 with the perforated 

 pipe method, and $12 to S 13 with the inverted pan method. 

 For these figures and other facts here quoted, we are 

 indebted to Circular 151 of the Ohio Agricultural Experi- 

 ment Station, Wooster, Ohio, published in January, 

 1915. 



